For the rotation of saw blades in annular saws, either gear-wheel drive or friction drive is used. Drive systems which are based on the former principle are described, for example, in the U.S. Pat. Nos. 2,804,105, 2,972,363, 3,373,489, and 3,808,685. Friction transmissions for the drive of annular saw blades are described, for example, in the U.S. Pat. Nos. 3,221,783, 3,438,410, and 3,930,310. The advantage of gear-wheel drive is that it is very reliable and moreover slipping can be avoided. A decisive disadvantage, however, is that the wear between the gear-wheel and the annular saw blade is very great, particularly when sawing in concrete, metal and other materials with heavy wear, since it is impossible to prevent sawdust from getting into the gear-wheel.
The systems hitherto developed which are based on friction-based transmissions use one or more driving wheels which bear against the plane web of the saw blade with opposite support from an opposing wheel at the other side of the saw blade. Since the special field of application of annular saws is for sawing in concrete, car bodies and similar demanding connections, for which saw blades equipped with diamonds are used, water must be sprayed on the object which is being sawn, or on the saw blade, to cool the saw blade and the diamonds and to flush away the sawdust as far as possible. It has been found that this spraying with water drastically reduces the friction between the driving wheel and the saw blade as a result of the fact that a film of water is formed between the driving wheel and the web of the saw blade. With known friction-based systems, there have also been problems with the drive, when the resistance to sawing was very great, even when no spraying with water occurs. In order to improve the friction and hence the drive, the driving wheel has been covered with a wearing surface. This has not solved the problem of water planing, however, and moreover has quickly worn out. Another method of increasing the friction is to increase the pressure between the driving wheel and the saw blade. This has resulted in so much development of heat, however, that the blade bends and the bearings of the driving wheel are demaged.